| Paper | Title | Page |
|---|---|---|
| MOPC049 | Comparative Study of Vibration Stability at Operating Light Source Facilities and Lessons Learned in Achieving NSLS II Stability Goals | 181 |
|
||
|
Understanding the correlation between storage ring vibration and electron beam oscillation is key in achieving the design beam parameters of a 3rd generation light source. Spectral properties of the vibration at the storage ring floor, in addition to amplitude, and its relation to the dynamic properties of the lattice govern the complex relation between lattice movement and beam jitter. Spectral characteristics are, in general, site-specific and motions exhibit spatial variability. To best describe the relationship between the ground motion field at the NSLS II site and the accelerator while quantifying the storage ring oscillations resulting from its interaction with the undisturbed site, field studies have been conducted at various light source facilities. By using the same metric data characterizing the achieved stability levels in operating light sources are generated and used in the assessment of the NSLS II stability which in turn linked to the specific site, subsurface and design characteristics. The paper summarizes the results of these comprehensive findings and presents an overall assessment of stability levels that can be achieved.
Work performed under the auspices of the US DOE. |
||
| MOPC050 | Ground Motion Studies at NSLS II | 184 |
|
||
|
In 3rd generation light sources such as the 3 GeV NSLS II under design at BNL, strict requirements associated with vibration on the storage ring floor are imposed in order to minimize the jitter in the electron beam. Spectral characteristics storage ring vibration and dynamic properties of the ring lattice are controlling parameters. Ground motion at the NSLS-II site is characterized by a complex spectrum consisting of fast and slow motions stemming from natural and cultural sources. Cultural noise with frequencies higher than a few Hz has the potential of dramatically affecting the accelerator performance. In this study, an array of vibration measurements at the undisturbed NSLS II site has been made in order to establish the “green-field” vibration environment and its spectral characteristics. Its interaction with the NSLS II accelerator structure and the quantification of the storage ring vibration, both in terms of amplitude and spectral content have been assessed through a state-of-the-art wave propagation and scattering analysis. This paper focuses primarily on the wave propagation and scattering aspect as well as on the filtering effects of accelerator structural parameters.
Work performed under the auspices of the US DOE. |
||
| MOPC093 | Experimental Study of Radiation Damage in Carbon Composites and Graphite Considered as Targets in the Neutrino Super Beam | 280 |
|
||
|
Carbon composites have been of primary interest as materials of choice for a multi-MW neutrino superbeam which desires low-Z pion production target. Beam on target experiments conducted at BNL made the case stronger in their favor, as compared to graphite, by demonstrating their excellent shock resistance which is directly linked with their extremely low thermal expansion. Since target survivability also depends on resistance to prolonged radiation, a series of irradiation damage studies on carbon composites and graphite were launched. While carbon composites at moderate doses exhibited interesting behavior of damage reversal through thermal annealing, at higher dose levels of peak proton fluences >5x1020 protons/cm2 they exhibited serious structural degradation. The experimental study also showed that graphite suffered similar damage when subjected to same fluence level. The paper discusses the findings of the experimental studies focusing on these materials and attempts to explain their structural degradation observed under high proton fluences given the excellent survivability record, especially of graphite, under high neutron fluences in nuclear reactor settings.
Work performed under the auspices of the US DOE. |
||
| MOPC094 | Irradiation Effects on the Physio-mechanical Properties of Super-alloys Characterized by Low Thermal Expansion | 283 |
|
||
|
In an effort to address the limitations on high power accelerator target performance prompted by the elevated dose levels and the associated irradiation damage, an experimental study has been undertaken to evaluate the potential applicability of super alloys characterized by low thermal expansion over certain thermal regimes. The intriguing properties associated with materials such as super-Invar and the “gum” metal (Ti-12Ta-9Nb-3V-6Zr-O) are observed in their un-irradiated state. Irradiations were performed using the 200 MeV protons of the BNL Linac and/or a neutron flux generated by the stopping of the primary 112 MeV protons upstream of the exposed super-alloys. The paper presents the post-irradiation analysis results which reveal interesting damage reversal by the super-invar and unexpected low threshold of radiation resistance by the “gum” metal.
Work performed under the auspices of the US DOE. |
||
| WEPC052 | Achieving Stability Requirements for Nanoprobe and Long Beam Lines at NSLS II. A Comprehensive Study | 2109 |
|
||
| Driven by beam stability requirements at the NSLS II synchrotron a comprehensive study has been launched seeking to provide assurances that nanometer level stability at critical x-ray beam-lines is achievable, given the vibration environment at the selected site. Through this effort which represents the integration of an array of field measurements and a state-of-the-art model of wave propagation, the stability of special NSLS II beam-lines that push the envelope of beam size is quantified. In particular, the effects of ground vibration at the NSLS II site are studied both deterministically and stochastically to account for the stochastic nature of the disturbances arriving at the site and interact with the ring and the experimental lines. Validated numerical models are utilized in an effort to guide the design of sensitive lines. The objective is to both minimize vibration amplification as well establish a relative stability envelope between the beam extraction and imaging locations of the sensitive NSLS II beam-lines. | ||
| WEPC053 | An Experimental Study of Radiation-induced Demagnetization of Insertion Device Permanent Magnets | 2112 |
|
||
|
High brilliance in the 3GeV new light source NSLS II is obtained from the high magnetic fields in insertion devices (ID). The beam lifetime is limited to 3h by single Coulomb scattering in the Bunch (Touschek effect). This effect occurs everywhere around the circumference and there is unavoidable beam loss in the adjacent low-aperture insertion devices. This raises the issue of degradation and damage of the permanent magnetic material by irradiation with high energy electrons and corresponding shower particles. It is expected that IDs, especially those in-vacuum, would experience changes resulting from exposure to gamma rays, x-rays, electrons and neutrons. By expanding an on-going material radiation damage study at BNL the demagnetization effect of irradiation consisting primarily of neutrons, gamma rays and electrons on a set of NdFeB magnets is studied. Integrated doses of several Mrad to a few Grad were achieved at the BNL Isotope Facility with a 112-MeV, 90-uA proton beam. Detailed information on dose distributions and particle energy spectra on the NdFeB magnets was obtained with the MARS15 Monte-Carlo code. This paper summarizes the results of this study.
Work performed under the auspices of the US DOE. |